Field of the Invention
The invention relates to a hydraulic actuation device for a brake device of a wind turbine, comprising a hydraulic control line, which runs from a connection for a hydraulic system circuit of a wind turbine to a connection for at least one brake cylinder of a brake device, wherein at least one restrictor or orifice is arranged in the control line. The invention further relates to a corresponding brake device, to a wind turbine, and to a method for braking a shaft of a wind turbine.
The invention relates to the field of rotor brakes for wind turbines. These are typically equipped so that a brake disk, which can be braked by hydraulically controlled brake cylinders using brake shoes, is arranged at a fast shaft of a drive train which is driven by a rotor shaft via a gear box.
The brake is actuated during operation in order to stop the rotor in the event of specific serious disturbances or upon actuation of the emergency stop switch. It is also essential to securely brake the rotor for maintenance and repair work.
Braking occurs with active brake systems in that pressure is applied to the brake cylinders, and thereby the brake cylinders are extended until the brake shoes of the brake cylinder rest against, and brake, the brake disk. In order to prevent the full system pressure, which can amount to approximately 100 bar, from abruptly being present at the brake when actuating the rotor brake, a throttle is typically inserted in the pressure line. Thereby, the pressure only increases slowly at the brake, and vibrations in the system, which arise due to sudden speed variations as a result of strong braking, are avoided.
With this operating control of the rotor brake, a delay time results in that initially the brake gap between the brake shoes and the brake disk must be overcome. Only after the delay time, when the brake shoes contact the brake disk, a braking torque develops at the rotor brake disk.
The delay time also increases due to increasing wear. For this purpose, there are brake systems which compensate at least for the wear using a brake lining tracking system, and set a defined distance for the lining to the brake disk. The path, which must be overcome, before the brake disk is contacted by the brake lining is however not shortened by this.
The delay time, thus the duration from the moment at which the brake is requested, until it engages, amounts between approximately 0.3 and 7 seconds, and possibly up to 10 seconds, depending on the size of the brake gap and the type of the system. An appreciable braking torque develops only after this time.
The reaction of the brakes during emergency stop actuation is therefore relatively sluggish. In addition, in systems in which the brakes are also considered in the load design for limiting rotational speed or for rotational speed reduction, there is a risk that the brake performance is slower than in the design calculations. This can result in unexpected loads in the wind turbine.
Description of Related Art
An electrohydraulic brake module is known from the document EP 1 389 686 A1 that allows proportional brake control by means of a combination of a pressure limiting control valve actuatable by a proportional magnet and an actuatable switching valve, that maintains the generator set rotational speed at least in the event of a power failure. In the event of a power failure, in accordance with the present rotational speed, pressurizing medium is supplied via the switching valve into a working line, and/or via the control valve to a tank, in order to proportionally modulate the braking effect, wherein the proportional pressure limiting control valve performs the discharge control such that the generator maintains the set rotational speed.
The document DE 10 2004 057 522 A1 discloses a brake device for a wind turbine, in which a brake valve arrangement comprises a 3/2-way seat valve, via which a pressure chamber of a hydraulically actuatable brake cylinder is connected to a source of pressurizing medium for braking, and to a pressurizing medium sink for releasing the brake. The directional control seat valve allows a leak-free blocking of the brake cylinder.
The document EP 1 959 131 A2 relates to a wind turbine having a hydraulically actuatable rotor brake for a drive train, which has at least one hydraulically actuatable brake cylinder, the braking torque of which increases with increasing hydraulic pressure, wherein upon actuating the brake, a volume of hydraulic fluid is supplied through a pressure reducing valve into the brake cylinder and in the pressure line thereof, wherein a storage reservoir with hydraulic fluid is provided that is connected to the pressure line. Here, two pressure reducing valves are provided, one of which reduces a present system pressure to the brake pressure, and the other reduces the present system pressure to a holding pressure.